I am designing a data model for tourism-site. I have a table for places (countries, resorts, hotels) and a table for tours. The tables are pretty different in fields so the cant be merged into one. Both of them have usual auto_increment as id. Places and tours have photos so there is a third table for photos. This table has ‘parent’ field in which I plan to store the parent (place or tour) id.
Which is the best way to design these tables? One table for all photos and two tables as ‘parents’ for the photos. For now I have added ‘parent_type’ column to photos table, so when my script displays a tour it calls photos by its (parent) id and type (parent_type) ‘tour’ from the photos table…
Upd:
Is there a more graceful solution? With just 3 tables and no ‘parent_type’ column?
(cant post a diagram… here’s the link http://share.xmind.net/yentsun/tourism-site-data-model/)
There are no Parents involved – you just have photos with two atttributes – Place and Tour.
So use a Photos table with two foreign keys, one for Tour, the other for Place. And then of course
a Tours table and a Places table.
If you need to know which Tours went to which Places, deal with it directly with a Tour_Places table
which justifies itself independently.
As for “Parentness”, this solution still lets you identify, for a Tour (or Place), which Photos are associated.